Low-Energy QCD: Few-Nucleon Research at TUNL

Abstract

The main goal of few-nucleon research at the Triangle Universities Nuclear Laboratory (TUNL) is to perform high-precision measurements that contribute to advancing ab-initio calculations and testing nucleon-interaction models. The current focus is on the three-nucleon system, which has highly developed theory and has sufficient complexity to exhibit influences of three-nucleon forces.The few-nucleon measurements performed at the High Intensity Gamma-ray Source (HIGS) and in the tandem lab provide complementary information. We have performed the first exclusive differential cross-section measurements for photodisintegration of 3He at low energy. The measurements were carried out at an incident beam energy of 15 MeV. A difference in the 1S0 neutron-proton scattering length determined in this reaction from the value established by two-nucleon scattering data would be potential evidence for three-nucleon interactions that are not included in current calculations. The strength of the neutron-neutron (nn) 1S0 interaction is directly evaluated using nn quasi-free scattering in neutron-deuteron breakup. We are performing measurements of this process at two incident neutron beam energies, 10 and 16 MeV, using substantially different detector setups. The experiment methods and preliminary results of these experiments will be presented.